Subterranean “sliding” drilling operation typically involves rotating a drill bit on a downhole motor at the remote end of a drill pipe string. Drilling fluid forced through the drill pipe rotates the motor and bit. The assembly is directed or “steered” from a vertical drill path in any number of directions, allowing the operator to guide the wellbore to desired underground locations. For example, to recover an underground hydrocarbon deposit, the operator may drill a vertical well to a point above the reservoir and then steer the wellbore to drill a deflected or “directional” well that penetrates the deposit. The well may pass horizontally through the deposit. Friction between the drill string and the bore generally increases as a function of the horizontal component of the bore, and slows drilling by reducing the force that pushes the bit into new formations.
Such directional drilling requires accurate orientation of a bent segment of the downhole motor that drives the bit. Rotating the drill string changes the orientation of the bent segment (e.g., the direction of the well being drilled and/or the “toolface”). Toolface control may be automated. Automated toolface controls require sensing of the downhole toolface as a feedback measurement for the control loop. Such feedback may be received as measurement-while-drilling (MWD) measurements, such as from MWD magnetic toolface measurements, and MWD gravity toolface measurements. Such measurements are transmitted to a surface control system from downhole using telemetries such as mud pulse telemetry and/or electromagnetic (EM) telemetry.
Such toolface measurements require 10-30 seconds to reach the surface and thus are transmitted at speeds that are suboptimal for automated toolface controls. Current techniques attempt to work around such sampling rate issues by predicting toolface measurements based on changes in differential pressure. Accordingly, a relationship between differential pressure and downhole MWD measurements is constructed so that MWD measurements may be predicted based on differential pressure measurements instead. For third party MWD tools, however, construction of such a relationship is dependent on the expertise of the driller. As such, an inexperienced driller may construct a flawed relationship that may not accurately determine MWD measurements from differential pressure measurements and such a flawed relationship may be used for the duration of the operation of the tool without correction. This can lead to inefficiencies, mistakes, and delays in the drilling process.